For over two decades, I’ve traversed the world of welding, witnessing the magic of transforming raw materials into lasting creations. From intricate aerospace components to colossal shipbuilding projects, the silent conductor behind it all is often overlooked: the tungsten electrode. Unlike most blogs that provide a cursory overview, this post delves deeper –– exploring the science, history, and lesser-known secrets of these unassuming heroes. We’ll also unveil the unique characteristics of various tungsten electrode types, empowering you to make informed choices for superior welds.
A Legacy Forged in Innovation: The Evolution of Tungsten Electrodes
The story begins in the 1920s, a fledgling era of welding experimentation. Back then, welders grappled with carbon electrodes, which offered conductivity but introduced unwanted carbon contamination. Enter tungsten, a naturally occurring marvel boasting the highest melting point of any element –– the perfect candidate to withstand the fierce heat of the welding arc. The first tungsten electrodes were basic –– pure tungsten with no additives. While ideal for AC aluminium welding, their limitations emerged quickly. Pure tungsten struggled with arc stability on DC current and had a tendency to “spit” molten tungsten into the weld pool, compromising weld quality.
A Spectrum of Alloys: Unveiling the Tungsten Electrode Family
Necessity, as always, became the mother of invention. Alloyed tungsten electrodes emerged, incorporating small amounts of other rare earth elements like cerium, lanthanum, thorium, and zirconium. Each addition unlocked unique properties:
| Welding Mode | Tungsten Type | Colour |
|---|---|---|
| AC | Pure Tungsten | Green |
| DC or AC/DC | Ceriated 2% | Grey |
| DC or AC/DC | Lanathanated 1% | Black |
| DC or AC/DC | Lanathanated 1.5% | Gold |
| DC or AC/DC | Lanathanated 2% | Blue |
| DC | Thoriated 1% | Yellow |
| DC | Thoriated 2% | Red |
| AC | Zirconiated 1% | White |
Pure Tungsten (WP)
AWS A5.12 EWP, ISO 6848 WP
The OG of tungsten electrodes, offering excellent AC arc stability for aluminium welding. However, its limitations in DC welding and spitting tendencies make it less versatile.
Ceriated Tungsten (CeO2 – 1% or 2%)
AWS A5.12 EWCe-2, ISO 6848 WC20
A popular choice for DC welding of mild steel and stainless steel. Cerium increases arc stability and reduces spitting, offering good weld pool control. It’s also forgiving of less than perfect grinding techniques –– a boon for beginners.
Lanthanated Tungsten (La2O3 – 1.5% or 2%)
AWS A5.12 EWLa-, ISO 6848 WL
Another champion for DC welding, particularly for steels and nickel alloys. Lanthanum enhances arc stability and offers a wider operating range for amperage compared to ceriated tungsten. This translates to a more forgiving electrode when dealing with varying current demands.
Thoriated Tungsten (ThO2 – 1% or 2%)
AWS A5.12 EWTh-2, ISO 6848 WT20
(Use with caution due to radioactivity) The traditional workhorse for DC steel welding, offering superior arc stability and lower operating temperatures. However, due to growing concerns about thorium’s radioactivity, its use is declining in favor of safer alternatives like ceriated and lanthanated tungsten. (Always check local regulations and safety protocols before using thoriated tungsten electrodes.)
Zirconiated Tungsten (ZrO2 – 1.5% or 4%)
AWS A5.12 NONE, ISO 6848 WZ8
The champion for AC welding, particularly for aluminium and magnesium. Zirconium excels in arc stability and minimises tungsten inclusion in the weld pool, making it ideal for applications demanding the highest quality and minimal contamination.
Recommended Electrode current Guide
| Tungsten Size | DC-Electrode Negative | AC Symmetrical Wave | AC Un-symmetrical Wave |
|---|---|---|---|
| 1.0mm | 15 – 80A | 10 – 80A | 20 – 60A |
| 1.6mm | 70 – 150A | 70 – 150A | 60 – 120A |
| 2.4mm | 150 – 250A | 140 – 225A | 100 – 180A |
| 3.2mm | 250 – 400A | 225 – 325A | 160 – 250A |
| 4.0mm | 400 – 500A | 300 – 400A | 200 -320A |
| 6.0mm | 750 – 1000A | 500 – 630A | 340 – 525A |
Beyond the Basics: Choosing the Right Tungsten Electrode
Now, here’s where most blogs stop. They simply list the different tungsten electrode types. But what they often miss is the crucial decision-making process. Selecting the right electrode goes beyond just the material. Here are some crucial factors to consider:
- Current Type (AC/DC): AC or DC? This is the first question. Pure and zirconiated tungsten excel in AC, while thoriated, ceriated, and lanthanated shine in DC.
- Material to be Welded: Stainless steel? Aluminium? Each material has its preferred tungsten electrode type for optimal results.
- Base Metal Thickness: Thin sheets demand a finer electrode for better control, while thicker plates can handle larger diameters.
- Amperage: Higher amperage applications require electrodes with better current-carrying capacity to prevent overheating and electrode tip deterioration.
The Art of the Grind: Sharpening Your Expertise
Finally, a lesser-known but highly impactful aspect – the grind. The grind profile of your tungsten electrode significantly affects arc characteristics and penetration. A pointed grind offers a sharp, focused arc for narrow welds, while a blunted grind creates a wider, softer arc for thicker materials. Mastering the art of grinding your tungsten electrodes takes practice, but it unlocks a whole new level of control over your welds.
By understanding the science behind tungsten electrodes, the history of their development, and the key factors influencing their selection, you transform yourself from a welder into a welding artist. So next time you pick up a TIG torch, remember the silent hero – the tungsten electrode – and wield it with the knowledge and expertise it deserves. After all, a great weld starts with the right foundation.
Browse our range of Tungsten Electrodes
FAQs
What are tungsten electrodes used for?
Tungsten electrodes are the workhorse conductors in two key metal joining processes: Tungsten Inert Gas (TIG) welding and Plasma Arc Welding (PAW). They excel in these applications due to their unique properties:
- High Melting Point: Tungsten boasts one of the highest melting points of all metals, exceeding 3,400°C (6,135°F). This allows it to withstand the intense heat of the welding arc without melting or vaporising significantly.
- Excellent Electrical Conductivity: Tungsten efficiently conducts electricity, essential for creating and sustaining the stable arc that heats the metal workpiece in TIG and plasma welding.
- Superior Arc Stability: Tungsten electrodes contribute to a focused and controllable arc during welding, leading to high-quality welds.
Is thoriated tungsten banned?
Thoriated tungsten electrodes are not universally banned, but their use is restricted or discouraged in many countries due to radioactivity concerns.
Here’s a breakdown of the situation:
- Thorium and Radioactivity: Thoriated tungsten electrodes contain thorium oxide, a radioactive material. When the electrode is ground or chipped, tiny particles can become airborne and potentially inhaled, leading to internal radiation exposure.
- Regulations and Recommendations: Due to these health risks, several countries and organisations have implemented regulations or recommendations regarding thoriated tungsten:
- Ban: Some countries have completely banned the manufacture, sale, and use of thoriated tungsten electrodes.
- Strict Regulations: Other countries impose strict regulations on their use, requiring specific handling procedures and personal protective equipment.
- Phasing Out: Even in regions without a ban, there’s a growing trend to phase out thoriated tungsten in favour of safer alternatives.
- Safer Alternatives: Several excellent non-radioactive tungsten electrode options are available, including lanthanated, ceriated, and zirconiated tungsten. These electrodes offer comparable performance characteristics without the radioactivity concerns.
Here’s what to consider when working with thoriated tungsten:
- Check Local Regulations: Always research and comply with any local regulations regarding thoriated tungsten use in your area.
- Safer Alternatives: If possible, prioritise using safer, non-radioactive tungsten electrode varieties like lanthanated or ceriated.
- Proper Handling: If thoriated tungsten is your only option, ensure proper ventilation and wear appropriate respiratory protection while using a tungsten grinder or sharpener or handling the electrodes.
How radioactive is 2-thoriated tungsten?
2-thoriated tungsten isn’t necessarily “highly” radioactive, but it does pose a health risk if not handled properly. Here’s a breakdown:
- Low External Radiation: The good news is the tungsten matrix in thoriated electrodes effectively shields most of the radiation emitted by thorium. This means minimal external radiation exposure during normal handling.
- The Danger Lies in Inhalation: The primary concern is with inhaled thoriated particles. Grinding or chipping the electrode can release tiny particles containing thorium oxide dust. If inhaled, these particles can lodge in the lungs and potentially lead to internal radiation exposure over time.
- Activity Levels: The radioactivity of a thoriated tungsten electrode is measured in Becquerel (Bq). A typical 2% thoriated electrode might have an activity of around 3-7 kBq (kilobecquerel). This is relatively low compared to some sealed radioactive sources, but it’s still important to be cautious.
Key Points to Remember:
The main risk with thoriated tungsten is from inhaling dust particles during grinding, chipping, or welding (if fumes are inhaled).
Proper ventilation and respiratory protection are crucial when working with thoriated tungsten, especially during grinding.
Safer Alternatives: Whenever possible, consider using safer, non-radioactive tungsten electrodes like lanthanated or ceriated types.
